A jack-up rig is a type of mobile offshore oil and gas drilling platform that is able to stand still on the sea floor, resting on a number of supporting legs. The most popular design uses 3 legs. The supporting columns may be moved up and down by a hydraulic or electrical system. The whole rig can also be jacked up when the supporting legs touch the seafloor. During transit, the platform floats on its hull and is typically towed to a new location by offshore tugs. Jackup rigs provide platforms that are more stable than semisubmersible platforms but can only be placed in relatively shallow waters, generally less than 1,000 feet (300 m) of water. The rig acts as a kind of platform. This type of rig is almost always used in connection with oil and/or natural gas drilling.